package 链表;

public class _141_环形链表 {

	public boolean hasCycle(ListNode head) {
		if (head == null || head.next == null) {
			return false;
		}
		ListNode slow = head;
		ListNode fast = head.next;
		while (fast.next != null && fast != null) {
			slow = slow.next;
			fast = fast.next.next;
			if (slow == fast) {
				return true;
			} 
		}

		return false;
	}
}
